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    NaugaNeedles now offers tuning fork based probes for scanning probe microscopy (SPM) applications.

     Figure 1-a shows schematic of this unique product. In this device, the tuning fork is used for force feedback. The device also has a conductive tip that can be connected to the electronic readout (for conductive AFM or Tunneling current readout) without cross talking with the fork electrodes. As shown in Figure 1-a, the tip is located vertical to the fork prong. Using proper insulating and metallic coating, a conductive pad is coated at the edge of the fork prong that provides electrical readout to the tip. For that, prior to tip attachment, the entire quartz fork is coated with an insulating material. Then, the top of one of the prong is coated with metal and the needle is attached to the edge of the metal coated prong. Such device can be used for AFM/STM that can detect the tunneling current or in conductive mode AFM while using the tuning fork as force feedback for AFM scanning.
    Since the amount of mass added to the fork is minimal, the resonance frequency spectrum does not change notably. As shown in Figure 1-b the resonance frequency of the tuning fork is still around 32.6 KHz and the Q factor is around 1,200 in ambient condition.

Figure 1 a) The schematic of tuning fork based SPM probe from NaugaNeedles. b) The resonance frequency spectrum of the device after tip attachment and insulation. Courtesy of RHK

These tuning fork probes can be mounted on different carrier. We are able to design and engineer tuning fork on any type of carrier in the market. We are also willing to work with our customers in design and building custom made probes.

Various types of tip material can be offered. As shown in Figure 3, currently we offer three types of tip material on the edge of the fork prong: a) Tungsten wire between 50-500 µm long (can be adjusted per customer request) and 20 to 50 nm in radius of curvature, b) Standard silicon AFM cantilever tips coated with metal.

Figure 3 Different types of probes attached to a prong of a Tuning Fork.